Performances in the Iowa Gambling Task and the facial emotion recognition test will be compared between ET patients and controls. All study subjects will also be tested with the following battery: Modified Card Sorting Test, Stroop, Trail Making Test and Verbal Fluency, Beck Depression Inventory and the Mattis Dementia Rating Scale. These tests will allow assessing the impact of executive function, depression and memory loss on performances in the Iowa Gambling Task and the facial emotion recognition test. Finally, performances in the Iowa Gambling Task and the facial emotion recognition test will be related to sex, age, disease duration and tremor severity.